U.S. patent application number 16/957164 was filed with the patent office on 2021-08-12 for on-bed state monitoring system and bed including same.
The applicant listed for this patent is Minebea Mitsumi Inc.. Invention is credited to Norihito IIDA, Toshiaki NISHIMURA.
Application Number | 20210244361 16/957164 |
Document ID | / |
Family ID | 1000005599977 |
Filed Date | 2021-08-12 |
United States Patent
Application |
20210244361 |
Kind Code |
A1 |
IIDA; Norihito ; et
al. |
August 12, 2021 |
ON-BED STATE MONITORING SYSTEM AND BED INCLUDING SAME
Abstract
A present-in-bed state monitoring system (100) configured to
monitor a present-in-bed state of a subject on a bed (BD) includes:
a plurality of load detectors (11, 12, 13, 14) configured to be
provided on the bed or under legs of the bed to detect a load of
the subject; a center of gravity position calculating unit (31)
configured to calculate a center of gravity position of the subject
based on the detected load of the subject; a waveform output unit
(32) configured to output a waveform including a respiratory
waveform of the subject based on a temporal variation of the
calculated center of gravity position; a center of gravity position
determining unit (332) configured to determine whether or not the
center of gravity position is in an edge area of the bed; a body
motion determining unit (331) configured to determine whether or
not the subject has a body motion based on the waveform including
the respiratory waveform of the subject, the body motion being
different from a respiration of the subject; and a notifying unit
(5) configured to perform a notification about the present-in-bed
state of the subject based on a determination result of the body
motion determining unit and a determination result of the center of
gravity position determining unit.
Inventors: |
IIDA; Norihito;
(Sagamihara-shi, Kanagawa, JP) ; NISHIMURA; Toshiaki;
(Kokubunji-shi, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Minebea Mitsumi Inc. |
Nagano |
|
JP |
|
|
Family ID: |
1000005599977 |
Appl. No.: |
16/957164 |
Filed: |
December 26, 2018 |
PCT Filed: |
December 26, 2018 |
PCT NO: |
PCT/JP2018/047899 |
371 Date: |
August 25, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/0816 20130101;
A61B 5/1121 20130101; A61B 5/746 20130101; A61B 5/7405 20130101;
A61B 2562/0252 20130101; A61B 5/6892 20130101; A61B 5/742
20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 5/11 20060101 A61B005/11; A61B 5/08 20060101
A61B005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2017 |
JP |
2017-252848 |
Claims
1. A present-in-bed state monitoring system configured to monitor a
present-in-bed state of a subject on a bed, the system comprising:
a plurality of load detectors configured to be provided on the bed
or under legs of the bed to detect a load of the subject; a
controller configured to control the present-in-bed monitoring
system to: calculate a center of gravity position of the subject
based on the detected load of the subject; output a waveform
including a respiratory waveform of the subject based on a temporal
variation of the calculated center of gravity position; determine
whether or not the center of gravity position is in an edge area of
the bed; and determine whether or not the subject has a body motion
based on the waveform including the respiratory waveform of the
subject, the body motion being different from a respiration of the
subject; and a notifying unit configured to perform a notification
about the present-in-bed state of the subject based on a
determination result of the determining of whether or not the
subject has the body motion and a determination result of the
determining of whether or not the center of gravity position is in
the edge area of the bed wherein the controller is further
configured to cause the notifying unit to perform the notification
based on the determination result of the determining of whether or
not the subject has the body motion and the determination result of
the determining of whether or not the center of gravity position is
in the edge area of the bed, and wherein the controller causes the
notifying unit to perform a first notification in a case that the
center of gravity position is determined to be in the edge area of
the bed and the subject has determined to have the body motion, and
causes the notifying unit to perform a second notification
different from the first notification in a case that the center of
gravity position is determined to be in the edge area of the bed
and the subject is determined not to have the body motion.
2. (canceled)
3. The present-in-bed state monitoring system according to claim 1,
wherein the controller determines whether or not the subject has a
large body motion involving a movement of a trunk of the subject,
and the controller causes the notifying unit to perform the first
notification in a case that the center of gravity position is
determined to be in the edge area of the bed and the subject is
determined to have the large body motion.
4. The present-in-bed state monitoring system according to claim 1,
wherein the controller determines whether or not the subject has
the body motion different from the respiration of the subject,
based on an amplitude of the waveform including the respiratory
waveform of the subject.
5. The present-in-bed state monitoring system according to claim 1,
wherein the controller is further configured to determine whether
or not the subject is present on the bed based on the respiratory
waveform.
6. The present-in-bed state monitoring system according to claim 1,
wherein the notifying unit includes a monitor configured to perform
the notification by an image, and a speaker configured to perform
the notification by an audio.
7. A bed system comprising: a bed; and the present-in-bed state
monitoring system as defined in claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a present-in-bed state
monitoring system (on-bed state monitoring system) provided with a
plurality of load detectors, and to a bed provided with the
abovementioned system.
BACKGROUND ART
[0002] For the sites of medical treatment and caregiving, it is
proposed to determine a state of a (human) subject on the basis of
such a (body weight) load of the subject on a bed as detected by
load detectors. In particular, for example, it is proposed to
determine whether the subject is present in the bed or absent from
the bed, estimate the respiratory rate of the subject, etc., on the
basis of the detected load.
[0003] Patent Literature 1 discloses a method for detecting a
present-in-bed situation for the bed to notify the information that
the in-bed position of the subject is located in an end part area
(edge area) of the bedding portion of the bed, on the basis of
detecting of the load applied on the bedding portion of a bed with
four load detecting means and a determining step carried out by
fitting the load values outputted from the four load detecting
means into a plurality of determination formulas.
CITATION LIST
[0004] Patent Literature 1: Japanese Patent No. 4965904
SUMMARY
Technical Problem
[0005] In the sites of medical treatment and caregiving, manpower
is often not sufficient. Therefore, with the method for detecting a
present-in-bed situation for the bed as disclosed in Patent
Literature 1, it is desired to further prevent mistaken
notifications.
[0006] An object of the present invention is to provide a
present-in-bed state monitoring system and a bed provided with the
abovementioned system capable of: determining a present-in-bed
state of a subject on the bed with high precision, and notifying a
user of the result determined above.
Solution to the Problem
[0007] According to a first aspect of the present invention, there
is provided a present-in-bed state monitoring system configured to
monitor a present-in-bed state of a subject on a bed, the system
including:
[0008] a plurality of load detectors configured to be provided on
the bed or under legs of the bed to detect a load of the
subject;
[0009] a center of gravity position calculating unit configured to
calculate a center of gravity position of the subject based on the
detected load of the subject;
[0010] a waveform output unit configured to output a waveform
including a respiratory waveform of the subject based on a temporal
variation of the calculated center of gravity position;
[0011] a center of gravity position determining unit configured to
determine whether or not the center of gravity position is in an
edge area of the bed;
[0012] a body motion determining unit configured to determine
whether or not the subject has a body motion based on the waveform
including the respiratory waveform of the subject, the body motion
being different from a respiration of the subject; and
[0013] a notifying unit configured to perform a notification about
the present-in-bed state of the subject based on a determination
result of the body motion determining unit and a determination
result of the center of gravity position determining unit.
[0014] The present-in-bed state monitoring system according to the
first aspect may further include a notification control unit
configured to cause the notifying unit to perform the notification
based on the determination result of the body motion determining
unit and the determination result of the center of gravity position
determining unit, wherein the notification control unit may cause
the notifying unit to perform a first notification in a case that
the center of gravity position determining unit determines that the
center of gravity position is in the edge area of the bed and the
body motion determining unit determines that the subject has the
body motion, and may cause the notifying unit to perform a second
notification different from the first notification in a case that
the center of gravity position determining unit determines that the
center of gravity position is in the edge area of the bed and the
body motion determining unit determines that the subject does not
have the body motion.
[0015] In the present-in-bed state monitoring system according to
the first aspect, the body motion determining unit may determine
whether or not the subject has a large body motion involving a
movement of a trunk of the subject, and the notification control
unit may cause the notifying unit to perform the first notification
in a case that the center of gravity position determining unit
determines that the center of gravity position is in the edge area
of the bed and the body motion determining unit determines that the
subject has the large body motion.
[0016] In the present-in-bed state monitoring system according to
the first aspect, the body motion determining unit may determine
whether or not the subject has the body motion different from the
respiration of the subject, based on an amplitude of the waveform
including the respiratory waveform of the subject.
[0017] The present-in-bed state monitoring system according to the
first aspect may further include a present-in-bed determining unit
configured to determine whether or not the subject is present on
the bed based on the respiratory waveform.
[0018] In the present-in-bed state monitoring system according to
the first aspect, the notifying unit may include a monitor
configured to perform the notification by an image, and a speaker
configured to perform the notification by an audio.
[0019] According to a second aspect of the present invention, there
is provided a bed system including a bed and the present-in-bed
state monitoring system according to the first aspect.
Effects of the Invention
[0020] The present-in-bed state monitoring system and the bed
provided with the abovementioned system according to the present
invention can determine the present-in-bed state of the subject on
the bed with high precision, and can notify a user of the result
determined above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a block diagram depicting a configuration of a
present-in-bed state monitoring system according to an embodiment
of the present invention.
[0022] FIG. 2 is an illustrative view depicting an arrangement of
load detectors for a bed.
[0023] FIG. 3 is a flow chart depicting a method for monitoring a
present-in-bed state by using the present-in-bed state monitoring
system.
[0024] FIG. 4A is an illustrative view depicting a body axis of a
subject, and an aspect of respiratory oscillation (vibration) along
a body axis direction.
[0025] FIG. 4B depicts an example of a respiratory waveform drawn
on the basis of the respiratory oscillation.
[0026] FIG. 5 is a block diagram depicting a configuration of a
present-in-bed state monitoring unit.
[0027] FIG. 6 is a flow chart depicting a procedure of a
present-in-bed state monitoring step.
[0028] FIG. 7A depicts an example of waveform including a
respiratory waveform when a small body motion arises in the
subject.
[0029] FIG. 7B depicts an example of waveform including a
respiratory waveform when a large body motion arises in the
subject.
[0030] FIG. 8 depicts an example of bed edge areas set on the bed
BD.
[0031] FIG. 9 is a flow chart depicting a procedure of a
present-in-bed state monitoring step according to a modified
embodiment of the present invention.
[0032] FIG. 10 is a block diagram depicting an overall
configuration of a bed system according to another modified
embodiment of the present invention.
DESCRIPTION OF EMBODIMENT
Embodiment
[0033] Referring to FIGS. 1 to 8, an explanation will be made on an
embodiment of the present invention.
[0034] As shown in FIG. 1, a present-in-bed state monitoring system
100 of this embodiment primarily has a load detecting unit 1, a
control unit 3, a storage unit 4, and a notifying unit 5. The load
detecting unit 1 and the control unit 3 are connected via an A/D
converting unit 2. The control unit 3 is further connected to an
input unit 6.
[0035] The load detecting unit 1 includes four load detectors 11,
12, 13, and 14. Each of the load detectors 11, 12, 13, and 14 is a
load detector for detecting a load by using, for example, a
beam-type load cell. Such a load detector is disclosed, for
example, in Japanese Patent No. 4829020 and Japanese Patent No.
4002905. Each of the load detectors 11, 12, 13, and 14 is connected
to the A/D converting unit 2 by way of wiring.
[0036] The four load detectors 11, 12, 13, and 14 of the load
detecting unit 1 are arranged under legs of a bed used by a
subject. In particular, as depicted in FIG. 2, the load detectors
11, 12, 13, and 14 are arranged respectively under casters C.sub.1,
C.sub.2, C.sub.3, and C.sub.4 fitted on the lower ends of the legs
at the four corners of the bed BD.
[0037] The A/D converting unit 2 includes an A/D convertor
connected respectively to the load detecting unit 1 and the control
unit 3 by way of wiring, to convert analog signals from the load
detecting unit 1 to digital signals.
[0038] The control unit 3 is a dedicated or general-purpose
computer inside which a center of gravity position calculating unit
31, a waveform output unit 32, and a present-in-bed state
monitoring unit 33 are constructed.
[0039] The storage unit 4 is a storage device for storing data used
in the present-in-bed state monitoring system 100 and, for example,
can use a hard disk (magnetic disk) for that purpose. The notifying
unit 5 includes a monitor 51 such as a liquid crystal monitor or
the like for visual (image) notification on the basis of the output
from the control unit 3, and a speaker 52 for auditory notification
also on the basis of the output from the control unit 3.
[0040] The input unit 6 is an interface for performing
predetermined inputs for the control unit 3, which may be a
keyboard and a mouse.
[0041] An explanation will be made on an operation of monitoring
the present-in-bed state of the subject on the bed by using such
present-in-bed state monitoring system 100. In this context, to
monitor the present-in-bed state of the subject is, in particular
for example, to monitor whether or not the subject is in a
condition of a possible tumble or fall from the bed (to be referred
to below as "dangerous condition" as appropriate).
[0042] Monitoring the present-in-bed state of the subject by using
the present-in-bed state monitoring system 100 primarily includes:
as depicted in the flow chart of FIG. 3, a load detecting step S1
for detecting the (body weight) load of the subject; a center of
gravity position calculating step S2 for obtaining (finding) a
center of gravity position of the subject on the basis of the
detected load; a waveform output step S3 for outputting a waveform
including a respiratory waveform (to be described later on) on the
basis of a temporal variation of the center of gravity position of
the subject; and a present-in-bed state monitoring step S4 for
monitoring the present-in-bed state of the subject by using the
center of gravity position of the subject and the waveform
including the respiratory waveform of the subject.
[0043] [The Load Detecting Step]
[0044] In the load detecting step S1, the load detectors 11, 12,
13, and 14 are used to detect the load of the subject S on the bed
BD. Because the load detectors 11, 12, 13, and 14 are arranged
respectively under the casters C.sub.1, C.sub.2, C.sub.3, and
C.sub.4, the load applied on the upper surface of the bed BD is
detected dispersively by the four load detectors 11, 12, 13, and
14.
[0045] Each of the load detectors 11, 12, 13, and 14 detects the
load (a variation in load), and outputs the result as an analog
signal to the A/D converting unit 2. The A/D converting unit 2
converts the analog signal into a digital signal through a sampling
period of 5 milliseconds, for example, and then outputs the digital
signal (to be referred to below as "load signal") to the control
unit 3. Hereinafter, the term "load signals s.sub.1, s.sub.2,
s.sub.3, and s.sub.4" will be used to refer respectively to the
load signals obtained by way of the A/D converting unit 2
converting the analog signals outputted from the load detectors 11,
12, 13, and 14 into the digital format.
[0046] [Center of Gravity Position Calculating Step]
[0047] In the center of gravity position calculating step S2, the
center of gravity position calculating unit 31 calculates the
position G (X, Y) of the center of gravity G of the subject S on
the bed BD at a predetermined period T (for example, a period equal
to the sampling period of 5 milliseconds described above) on the
basis of the load signals s.sub.1 to s.sub.4 fed from the load
detectors 11 to 14 to obtain the position of the center of gravity
G of the subject S, and the temporal variation thereof (center of
gravity locus). In this case, (X, Y) indicates the coordinates on
the XY coordinate plane in which the X-axis extends in the
longitudinal direction of the bed BD and the Y-axis extends in the
lateral direction of the bed BD while the central portion of the
bed BD is the origin (FIG. 2).
[0048] The calculation of the position G (X, Y) of the center of
gravity G by the center of gravity position calculating unit 31 is
performed in accordance with the following operation. That is, G
(X, Y) is calculated in accordance with the following formulas
assuming that the coordinates of the load detectors 11, 12, 13, and
14 are (X.sub.11, Y.sub.11), (X.sub.12, Y.sub.12), (X.sub.13,
Y.sub.13), and (X.sub.14, Y.sub.14) respectively, and the detection
values of the load detectors 11, 12, 13, and 14 are W.sub.11,
W.sub.12, W.sub.13, and W.sub.14 respectively.
X = X 11 .times. W 11 + X 12 .times. W 12 + X 13 .times. W 13 + X
14 .times. W 14 W 11 + W 12 + W 13 + W 14 [ Formula .times. .times.
1 ] Y = Y 11 .times. W 11 + Y 12 .times. W 12 + Y 13 .times. W 13 +
Y 14 .times. W 14 W 11 + W 12 + W 13 + W 14 [ Formula .times.
.times. 2 ] ##EQU00001##
[0049] The center of gravity position calculating unit 31 obtains
the position G (X, Y) of the center of gravity G, and the temporal
variation thereof, i.e., the center of gravity locus after
calculating the position G (X, Y) of the center of gravity G at the
predetermined sampling period T on the basis of the formulas 1 and
2 described above. The result is stored, for example, in the
storage unit 4.
[0050] [Waveform Output Step]
[0051] In the waveform output step S3, the waveform output unit 32
draws the waveform including the respiratory waveform of the
subject S on the basis of the center of gravity locus.
[0052] Here, in the present specification and the present
invention, the term "respiratory waveform" refers to a waveform
exhibiting a respiratory state of the subject S, where time is
denoted on the horizontal axis while the depth of respiration is
denoted on the vertical axis. An example of the respiratory
waveform is a respiratory waveform W depicted in FIG. 4B.
[0053] In the respiratory waveform W, the point W.sub.max denoting
the depth at the maximum value corresponds to the point of time
when the subject S ends an expiration (or an inspiration), whereas
the point W.sub.min denoting the depth at the minimum value
corresponds to the point of time when the subject S ends an
inspiration (or an expiration). One period of the respiratory
waveform W corresponds to one cycle of the respiration.
[0054] Based on an observation of the respiratory waveform W, it is
possible to obtain such information about the subject S as the
respiratory rate, respiratory state (stable respiration, occurrence
of snore, occurrence of apnea, utterance, and the like),
respiratory capacity (or breathing capacity, or tidal volume), and
the like.
[0055] The respiratory waveform is outputted on the basis of the
flowing principle.
[0056] The respiration of human is performed by moving the chest
and the diaphragm to expand and shrink the lungs. In this context,
when the air is inhaled (or an inspiration is performed), i.e.,
when the lungs are expanded, the diaphragm is lowered downwardly,
and the internal organs are also moved downwardly. On the other
hand, when the air is expired (or an expiration is performed),
i.e., when the lungs are shrunk, the diaphragm is raised upwardly,
and the internal organs are also moved upwardly. The inventors of
the present invention have found out, from a research on the
respiration, that the center of gravity of the subject vibrates
approximately along the up/down direction of the subject (the
backbone direction), i.e., along the body axis direction, due to
the up/down movement of the internal organs in accordance with the
respiration.
[0057] In the following description, the term "respiratory
oscillation (vibration)" is used to refer to such a vibration or
oscillation along the body axis direction of the subject in
accordance with the respiration of the subject. As depicted in FIG.
4A with two arrows, the center of gravity G of the subject S
oscillates along the direction of the body axis SA of the subject S
due to the respiratory oscillation.
[0058] In particular, for example, the respiratory waveform can be
obtained by plotting the locus of the respiratory oscillation on a
temporal area. That is, the respiratory waveform W of the subject S
is outputted by plotting the locus of the respiratory oscillation
of the subject S on a graphic area with the horizontal axis as the
time axis and with the vertical axis as the direction of the body
axis SA of the subject S.
[0059] In the present-in-bed state monitoring system 100 of this
embodiment, in particular, the waveform output unit 32 outputs the
waveform including the respiratory waveform W of the subject S in
the following manner. The waveform including the respiratory
waveform W refers to a waveform including the respiratory waveform
W, and a part deviating from the respiratory waveform due to a body
motion of the subject (to be described in detail later on).
[0060] The waveform output unit 32 outputs the waveform including
the respiratory waveform W of the subject S, based on the movement
of the center of gravity G of the subject S.
[0061] The respiratory waveform W is outputted in a period when it
is possible to catch the respiratory oscillation of the center of
gravity G. The center of gravity G also moves due to body motions
of the subject S other than the respiration, and the displacement
of the center of gravity G due to a body motion is far larger than
the amplitude of the respiratory oscillation. Therefore, it is only
possible to catch the respiratory oscillation, in practice, in a
period when there are no body motion arising in the subject S (to
be referred to below as "resting period" as appropriate), and the
respiratory waveform is outputted in the resting period.
[0062] Based on the locus of the center of gravity G, the waveform
output unit 32 starts to output the respiratory waveform at the
point of catching the respiratory oscillation (at the start point
of the resting period), or in particular for example, at the point
of having continuously observed the peaks. The respiratory waveform
is outputted with a peak of the respiratory oscillation as the
reference. Therefore, when there is a change in the amplitude of
the respiratory oscillation due to some change or the like in the
respiratory state of the subject, the center of the respiratory
waveform does not shift but, on the other hand, the change in the
amplitude is reflected.
[0063] If there is a body motion arising in the subject S, then a
deviation from the respiratory waveform occurs at that point (the
end point of a resting period). Then, when another resting period
comes, outputting the respiratory waveform W is started again.
[0064] The waveform output unit 32 may draw the outputted
respiratory waveform W on the monitor 51 of the notifying unit
5.
[0065] [Present-in-Bed State Monitoring Step]
[0066] In the present-in-bed state monitoring step S4, the
present-in-bed state monitoring unit 33 monitors the present-in-bed
state of the subject S, based on the position of the center of
gravity G calculated in the center of gravity position calculating
step S2, and the waveform including the respiratory waveform W
drawn in the waveform output step S3.
[0067] As depicted in FIG. 5, the present-in-bed state monitoring
unit 33 includes a body motion determining unit 331, a center of
gravity position determining unit 332, and a notification control
unit 333.
[0068] As depicted in FIG. 6, the present-in-bed state monitoring
step S4 includes a body motion determining step S41 for determining
whether or not the subject S has a body motion, a center of gravity
position determining step S42 for determining whether or not the
center of gravity of the subject S is in a bed edge area, a first
notifying step S43 to be carried out when the subject S has a body
motion and the center of gravity of the subject S is in the bed
edge area, and a second notifying step S44 to be carried out when
the subject S does not have a body motion but the center of gravity
of the subject S is in the bed edge area.
[0069] In the body motion determining step S41, the body motion
determining unit 331 determines whether or not the subject S has a
body motion, based on the waveform including the respiratory
waveform W of the subject S.
[0070] Here, a body motion of the subject S refers to a body
movement of the subject which is different from the respiration. In
particular, the body motion includes a "large body motion" and a
"small body motion".
[0071] In this specification and in the present invention, the
"large body motion" refers to a comparatively large one in the body
motion of the subject, along with a torso (trunk, body-trunk)
motion such as, in particular, a turn-over, get-up or the like. If
the subject performs a large body motion, then generally speaking,
the subject's body axis changes in orientation (orientation of the
extending backbone of the subject).
[0072] If the large body motion is defined from such a view of
point as exhibiting a temporal variation of the position of the
center of gravity, then generally it is possible to define the
large body motion as a movement of the center of gravity through a
comparatively long distance which is longer than a predetermined
distance within a predetermined period, that is, a body motion
where the center of gravity moves at a comparatively high speed. In
particular, for example, it is possible to define the large body
motion as a body motion where the movement of the center of gravity
occurs at a speed exceeding a predetermined value V. Alternatively,
on the basis of the difference from the temporal variation of the
position of center of gravity arising from the small body motion,
for example, it is also possible to define the large body motion as
a body motion to move the center of gravity through a distance
longer than a predetermined multiple of the distance of the
movement of the center of gravity due to the small body motion
within a predetermined length of time. Further, it may also be
defined by way of comparison to the amplitude of the respiratory
oscillation. In particular for example, it is possible to define
such a body motion as the large body motion as to give rise to a
movement of the center of gravity which exceeds a predetermined
multiple of the amplitude of the respiratory oscillation (the
respiratory waveform) in a predetermined period.
[0073] In this specification and in the present invention, the
"small body motion" refers to a comparatively small one in the body
motion of the subject, without the torso (trunk, body-trunk) motion
such as, in particular, the mere motion of a hand, a foot, the
head, and/or the like.
[0074] If the small body motion is defined from such a view of
point as exhibiting a temporal variation of the position of the
center of gravity, then generally it is possible to define the
small body motion as a movement of the center of gravity through a
comparatively short distance within a predetermined length of time,
that is, a body motion where the center of gravity moves at a
comparatively low speed. In particular, for example, it is possible
to define the small body motion as a body motion where the movement
of the center of gravity occurs at a speed of a predetermined value
v or so. Further, it may also be defined by way of comparison to
the amplitude of the respiratory vibration. In particular for
example, it is possible to define such a body motion as the small
body motion as to give rise to a movement of the center of gravity
which is about a predetermined multiple of the amplitude of the
respiratory oscillation (the respiratory waveform) in a
predetermined period. Further, the small body motion may also be
defined as a body motion giving rise to a movement of the center of
gravity excluding the oscillation in a certain direction, among the
movements of the center of gravity which fit into above
definitions. According to such a definition, when the movement of
the center of gravity is focused on, it is possible to more clearly
distinguish the small body motion from the respiration.
[0075] The following principle is applied to the determination of
whether or not there is a body motion on the basis of the waveform
including the respiratory waveform.
[0076] In the waveform output step S3, the waveform output unit 32
outputs the respiratory waveform W based on the respiratory
oscillation of the center of gravity G of the subject S, that is,
the oscillation of the center of gravity G in the direction of the
body axis S. Therefore, if the subject S has a body motion and the
center of gravity G of the subject S moves through a longer
distance than the amplitude of the respiratory oscillation, then
the deviation from the respiratory waveform W arises and, as
depicted in FIGS. 7A and 7B, the amplitude of the waveform
including the respiratory waveform W becomes large temporally.
[0077] FIG. 7A depicts an aspect of waveform including the
respiratory waveform W when a small body motion arises in the
subject S. FIG. 7B depicts an aspect of waveform including the
respiratory waveform W when a large body motion arises in the
subject S. If a small body motion arises in the subject S, then the
amplitude of the waveform including the respiratory waveform W is
larger than that of the respiratory waveform W during the resting
period, whereas if a large body motion arises in the subject S,
then the amplitude of the waveform including the respiratory
waveform W is even larger than that of the respiratory waveform W
when a small body motion arises in the subject.
[0078] The body motion determining unit 331 observes the waveform
including the respiratory waveform W, and determines that a body
motion (either a small body motion or a large body motion) has
arisen in the subject S, based on the fact that the amplitude of
the waveform including the respiratory waveform W has become as
large as exceeds a predetermined ratio in comparison with the
amplitude of the respiratory waveform W during the resting
period.
[0079] Further, generally speaking, a large body motion or a small
body motion arises in the subject in an irregular manner or at a
different period from that of the respiratory waveform W.
Therefore, if a large body motion or a small body motion arises in
the subject, then the waveform including the respiratory waveform W
may have a different period from that of the respiratory waveform W
or give rise to phasal deviation. Hence, based on the period or the
phase of the waveform including the respiratory waveform W, it is
possible for the body motion determining unit 331 to determine that
a body motion has arisen in the subject.
[0080] In the body motion determining step S41, if it is determined
that the subject S has a body motion, then the center of gravity
position determining unit 332 carries out the center of gravity
position determining step S42.
[0081] The center of gravity position determining unit 332
determines whether or not the center of gravity G of the subject S
is in either one of edge areas E of the bed BD (FIG. 8) at the
point when the subject S has a body motion. The width of either of
the edge areas E may be set at any possible value.
[0082] If the center of gravity G of the subject S is determined as
in either of the edge areas E in the center of gravity position
determining step S42, then the notification control unit 333
carries out the first notifying step S43.
[0083] In the first notifying step S43, the notification control
unit 333 notifies the user of the present-in-bed state monitoring
system 100 via the notifying unit 5 that there is a high degree of
risk of the subject S falling from the bed BD. In particular, for
example, a red icon is lit up on the monitor 51 and an alarm sound
is emitted via the speaker 52.
[0084] On the other hand, if the center of gravity G of the subject
S is determined as not in either of the edge areas E in the center
of gravity position determining step S42, then the body motion
determining step S41 is carried out again.
[0085] Even if it is determined that the subject S has not had a
body motion in the body motion determining step S41, the center of
gravity position determining unit 332 still carries out the center
of gravity position determining step S42. In this case, if the
center of gravity position determining unit 332 determines that the
center of gravity G of the subject S is in either of the edge areas
E of the bed BD, then the notification control unit 333 carries out
the second notifying step S44.
[0086] In the second notifying step S44, the notification control
unit 333 notifies the user of the present-in-bed state monitoring
system 100 via the notifying unit 5 that there is a possibility for
the subject S to fall from the bed BD. In particular, for example,
a yellow icon is lit up on the monitor 51 and a caution sound is
emitted via the speaker 52 to give an impression of emergency at a
lower level than the alarm sound emitted in the first notifying
step S43.
[0087] According to the knowledge of the inventors of the present
invention, the subject being asleep rarely falls from the bed
whereas the subject being awake may fall from the bed usually due
to failing in body control. Therefore, in the present-in-bed state
monitoring system 100 of this embodiment, notification is performed
to give an impression of emergency at a higher level for the first
notifying step S43 carried out when there is a body motion arising
in the subject S (that is, the subject S is presumed awake), than
for the second notifying step S44 carried out when there is no body
motion arising in the subject S (that is, the subject S is presumed
asleep).
[0088] The effects of the present-in-bed state monitoring system of
this embodiment are organized as follows.
[0089] The present-in-bed state monitoring system 100 of this
embodiment monitors the present-in-bed state of the subject S not
only by observing the position of the center of gravity G of the
subject S but also by taking into consideration whether or not the
subject S has a body motion, that is, whether or not the subject S
is in a resting state. Therefore, it is possible to determine, with
higher precision, that the subject S is at a risk of a possible
fall or the like, and to inform the user of the present-in-bed
state monitoring system 100 of that risk.
[0090] The present-in-bed state monitoring system 100 of this
embodiment can perform two different types of notification such as
alarm and caution via the notifying unit 5, according to the state
of the subject S. Therefore, the user of the present-in-bed state
monitoring system 100 can refer to the types of notification for
taking suitable response without excessive reaction.
[0091] The present-in-bed state monitoring system 100 of this
embodiment uses the waveform including the respiratory waveform W
of the subject S for monitoring the present-in-bed state of the
subject S. The respiratory waveform is outputted on the basis of
the respiration of the subject or, in other words, it is not
outputted if what is present on the bed is an inanimate object
(such as a bag, baggage, or the like). Therefore, according to the
present-in-bed state monitoring system 100 of this embodiment,
unnecessary monitoring possibly performed when an inanimate object
is placed on the bed, is prevented from being performed.
[0092] The present-in-bed state monitoring system 100 of this
embodiment outputs the respiratory waveform containing a lot of
information related to the respiratory state of the subject S,
draws a graph for the same on the monitor 51, and uses the waveform
including the respiratory waveform in determining whether or not
the subject S has a body motion and, consequently, in monitoring
the present-in-bed state of the subject S. That is, the
present-in-bed state monitoring system 100 of this embodiment is
configured to exhibit abundant respiratory information and monitor
the present-in-bed state with high precision, efficiently with a
simple system. Using this present-in-bed state monitoring system
100, the medical doctors and nurses can reliably observe the risk
of fall from the bed while monitoring the respiratory stability
and/or the respiratory state such as snores and the like of the
subject S.
[0093] The present-in-bed state monitoring system 100 of this
embodiment uses the load detectors 11 to 14 arranged under the legs
of the bed BD to monitor the present-in-bed state of the subject S
noninvasively. That is, with the present-in-bed state monitoring
system 100 of this embodiment, it is not necessary to attach any
measuring device to the body of the subject S so that the subject S
will not feel discomfort and a sense of incongruity.
MODIFIED EMBODIMENTS
[0094] It is possible to use the following modified embodiments
with respect to the present-in-bed state monitoring system 100 of
the above embodiment.
[0095] In the present-in-bed state monitoring system 100 of the
above embodiment, the present-in-bed state monitoring unit 33
determines whether or not the center of gravity G of the subject S
is in either of the edge areas E of the bed BD after firstly
determining whether or not the subject S has a body motion.
However, without being limited to that, as depicted in the flow
chart of FIG. 9, the present-in-bed state monitoring unit 33
according to a modified embodiment carries out the body motion
determining step S41 after carrying out the center of gravity
position determining step S42.
[0096] In particular, the present-in-bed state monitoring unit 33
of the modified embodiment first carries out the center of gravity
position determining step S42. Then, it carries out the body motion
determining step S41 if the center of gravity G of the subject S is
in either of the edge areas E, or carries out the center of gravity
position determining step S42 again if the center of gravity G of
the subject S is in neither of the edge areas E. If it is
determined that the subject S has a body motion in the body motion
determining step S41, then the first notifying step S43 is carried
out, whereas if it is determined that the subject S does not have a
body motion in the body motion determining step S41, then the
second notifying step S44 is carried out. As an example, the
contents of the first and second notifying steps S43 and S44 are
the same as in the above embodiment.
[0097] Further, the present-in-bed state monitoring unit 33
according to another modified embodiment may carry out the body
motion determining step S41 and the center of gravity position
determining step S42 at the same time. The present-in-bed state
monitoring unit 33 of another modified embodiment carries out the
first notifying step S43 if it is determined that the center of
gravity G of the subject S is in either of the edge areas E of the
bed BD and the subject S has a body motion, or carries out the
second notifying step S44 if it is determined that the center of
gravity G of the subject S is in either of the edge areas E of the
bed BD and the subject S does not have a body motion.
[0098] In the present-in-bed state monitoring system 100 of the
above embodiment, the body motion determining unit 331 of the
present-in-bed state monitoring unit 33 determines that the subject
S has a body motion if the subject S has either a small body motion
or a large body motion. However, without being limited to that, the
body motion determining unit 331 may determine that the subject S
has a body motion only when the subject S has a large body
motion.
[0099] For subject in some conditions (symptoms and the like), a
distinguish of the contents of notification based on the
present-in-bed state of the subject S (for example, the degree of
likelihood to fall) can be performed more appropriately, by
distinguishing carrying out the first notifying step S43 to perform
the first notification and carrying out the second notifying step
S44 to perform the second notification based on whether or not
there is a large body motion arising in the subject S as in the
above manner.
[0100] Based on the waveform including the respiratory waveform W,
for example, the body motion determining unit 331 of this modified
embodiment may determine that there is a large body motion arising
in the subject S if the amplitude of the waveform including the
respiratory waveform W becomes as large as exceeds a predetermined
ratio in comparison with the amplitude of the respiratory waveform
W during the resting period.
[0101] Note that in the waveform output step S3, when the waveform
output unit 32 outputs the respiratory waveform W, a bandpass
filter may be used to cancel the influence of movement of the
center of gravity G corresponding to a small body motion. By virtue
of this, it is possible to output the respiratory waveform W
without receiving the influence of a small body motion, thereby
allowing for determining whether or not there is a large body
motion with higher precision, on the basis of the waveform
including the respiratory waveform W.
[0102] The notification control unit 333 of the present-in-bed
state monitoring unit 33 of the above embodiment carries out a
display in the first notifying step S43 to give an impression of
emergency at a higher level than in the second notifying step S44.
However, without being limited to that, the notification control
unit 333 may carry out a notification in the second notifying step
S44 to give an impression of emergency at a higher level than in
the first notifying step S43. Further, according to the condition
of the subject S, it is possible to set other proper forms of
notification for the first and second notifying steps S43 and
S44.
[0103] Further, depending on the condition of the subject S
(symptoms and the like), for example, it may be sufficient to
perform a predetermined notification only if the center of gravity
position of the subject S is in either of the edge areas E of the
bed BD and there is a body motion arising in the subject S.
Therefore, in the present-in-bed state monitoring system 100 of the
above embodiment, the second notifying step S44 may be a step in
which no notification is performed at all (that is, the second
notifying step S44 may be omitted). Alternatively, the first
notifying step S43 may be a step in which no notification is
performed at all.
[0104] In the present-in-bed state monitoring system 100 of the
above embodiment, the present-in-bed state monitoring unit 33 may
have a present-in-bed determining unit for determining whether or
not the subject is present on the bed (present-in-bed
determination) on the basis of whether or not the respiratory
waveform is outputted. In this case, the present-in-bed state
monitoring unit 33 determines whether or not the subject is present
with the present-in-bed determining unit and, if the subject is
determined as present on the bed, then the present-in-bed state
monitoring step S4 may be started.
[0105] In the present-in-bed state monitoring system 100 of the
above embodiment, the load detectors 11, 12, 13, and 14 are not
limited to load sensors using beam-type load cells but, for
example, force sensors are also usable.
[0106] In the present-in-bed state monitoring system 100 of the
above embodiment, the number of load detectors is not limited to
four. It is also allowable to use five or more load detectors by
providing an additional leg or additional legs for the bed BD.
Alternatively, it is also allowable to arrange load detectors for
only three of the legs of the bed BD. Even when three load
detectors are used, it is still possible to detect the position of
the center of gravity G of the subject S on the plane of the bed BD
provided that the three load detectors are not arranged on a
straight line.
[0107] In the present-in-bed state monitoring system 100 of the
above embodiment, the load detectors 11, 12, 13, and 14 are
arranged respectively under the casters C.sub.1, C.sub.2, C.sub.3,
and C.sub.4 attached to the lower ends of the legs of the bed BD.
However, there is no limitation thereto. Each of the load detectors
11, 12, 13, and 14 may be provided respectively between one of the
four legs of the bed BD and the board of the bed BD. Alternatively,
if each of the four legs of the bed BD can be divided into upper
and lower portions, then each of the load detectors 11, 12, 13, and
14 may be provided between the upper portion of a leg and the lower
portion of the leg. Further alternatively, the load detectors 11,
12, 13, and 14 may be formed integrally with the bed BD to
construct a bed system BDS comprising the bed BD and the
present-in-bed state monitoring system 100 of this embodiment (FIG.
10). Note that in this specification, the "load detectors provided
on the bed" mean the load detectors each of which is provided
between one of the four legs of the bed BD and the board of the bed
BD as described above or the load detectors each of which is
provided between the upper portion of one leg and the lower portion
of the one leg.
[0108] In the present-in-bed state monitoring system 100 of the
above embodiment, it is also allowable to provide a signal
amplifying unit for amplifying the load signal fed from the load
detecting unit 1 and/or a filtering unit for removing noises from
the load signal, between the load detecting unit 1 and the A/D
converting unit 2.
[0109] In the present-in-bed state monitoring system 100 of the
above embodiment, the notifying unit 5 may include either the
monitor 51 or the speaker 52. Further, the notifying unit 5 may
include a printer for printing out the respiratory waveform, a
simplified visual display means such as lamps for performing the
first and second notifications, and/or the like, instead of the
monitor 51 or in addition to the monitor 51. Further, the notifying
unit 5 may include a vibration generating unit for performing the
notification by way of vibration, instead of the speaker 52 or in
addition to the speaker 52.
[0110] The present invention is not limited to the embodiment
described above provided that the feature of the present invention
is maintained. Other embodiments, which are conceivable within the
scope of the technical concept of the present invention, are also
included in the scope of the present invention.
INDUSTRIAL APPLICABILITY
[0111] According to the present-in-bed state monitoring system of
the present invention, based on the detection of the load value of
the subject, it is possible to monitor not only the respiratory
state but also the present-in-bed state of the subject, with high
precision and in a noninvasive manner. Therefore, if the system is
used in hospitals, caregiving facilities and the like, then it is
possible to preferably prevent the subject such as an inpatient, a
caregiving facility resident, or the like from falling from the bed
without giving the user any excessive burden and without giving the
subject any discomfort.
PARTS LIST
[0112] 1: load detecting unit, 11, 12, 13, 14: load detector, 2:
A/D converting unit, 3: control unit, 31: center of gravity
position calculating unit, 32: waveform output unit, 33:
present-in-bed monitoring unit, 4: storage unit, 5: display unit,
51: monitor, 52: speaker, 6: input unit, 100: present-in-bed state
monitoring system, BD: bed, BDS: bed system, S: subject.
* * * * *